Method and apparatus for recovering metal values



Aug. 30, 1938. E. B. MYERS 2,128,313

METHOD AND APPARATUS FOR RECOVERING METAL VALUES Original Filed March12, 1935 2 Sheets-Sheet 1.

Aug. 30, 1938. E. B. MYERS 2,128,313

METHOD AND APPARATUS FOR RECOVERING METAL VALUES original Filed March12, 1955 2 sheets-sheet 22l I? /J as i .4 l v 34 1N VENTOR.

I In" Patented Aug. 3i), 1938 UNITED STATES METHOD AND APPARATUS FORRECOVER- ING METAL VALUES Elman B. Myers, Montreal, Quebec, Canada, as-

signor to Myers Mill Corporation, Montreal, Quebec, Canada, acorporation of Quebec, Canada Application March 12, 1935, Serial No.10,652 Renewed July 15, 1938 15. Claims.

My present invention relates generally to metallurgy, and has particularreference to a new method and apparatus for recovering gold, silver,platinum, and other metal values from ore.

The present method and apparatus is fundamentally of the amalgamationtype, the metal values being recovered from the ore by causing anamalgamation thereof with mercury, and a subsequent separation of thesame from the mercury.

It is a general object of my invention to provide a method and apparatuswhich is of greatly simplil'led character, entirely feasible andpractical, and involving an unusually small expense in cost of equipmentand in operating costs. For example, an apparatus constructed inaccordance with my present invention can be made to operate on anentirely practical and commercial scale at a cost as low as 22o per tonof ore, and within an area of such compactness that no more than fifteenfeet separate the point at which raw ore is introduced and the point atwhich the gold or other metal values are recovered.

My invention is characterized by a procedure which involves colloidizingthe ore in a liquid dis- 25 persion medium, percolating the ore througha body of mercury, and exerting upon the tailings a maintained,high-voltage, electrolytic pressure toward the mercury. In a preferredmethod and apparatus, the foregoing procedural steps are coupled with acontinuous subjection of the mercury to a rehabilitation which puriesthe mercury and separates out the metal values that are sought.

The successful accomplishment of the present objectives relies in partupon the special manner in which the ore is colloidized; the manner inwhich it is percolated through the mercury; the manner in which theelectrolytic pressure is exerted; and, in part, upon the propercorrelation of these individual procedures` For example, I

have found it to be highly important that the ore be reduced to trulycolloidal form, as distinguished from the mere suspensions which arefrequently loosely referred to as being colloidal. It is important thatthe ore be colloidized by a method and machine which involves abrasion,and which produces colloidal particles no larger than approximately onemicron.

While it is possible that other methods or apparatus may be employed forthus colloidizing the ore, I have found the present desirable results tobe best accomplished by the use of a colloid mill of the flexible rotortype described and claimed by me in my earlier application Serial Number301,804, filed August 24, 1928 (presently to issue as Patent Number1,995,549). My present invention is, however, not limited to anyspecific method or means for colloidization, as long as the individualparticles are of a size less than one micron. It is to be understood,therefore, that the present invention is not limited to the employmentof any specific type of colloid mill; but it is also to be understoodthat the term colloid as used herein and in the appended claims isintended to refer to an attenuation of particles to the colloidal sizementioned.

One of the features of my invention lies in causing the ore(colloidized, as hereinbefore mentioned) to percolate through a body ofmercury, preferably to percolate upwardly through a coli umn of mercury.It is an important characteristic of the invention to provide a meansfor accomplishing the percolation in such a manner as to conduce towardamalgamation of the mercury with the colloidal particles of the metalthat is sought to be recovered. Thus, it is a feature of my invention toprovide a column of mercury of suflicient height to effect a materialretardation upon the percolation procedure, and to impose a substantialstatic pressure upon the individual colloidal particles that are passingthrough the column.

It is a further feature to provide a special means for further retardingthe percolation by means of perforated balfles or the like; and it is afurther feature to provide an arrangement for guiding the percolationtoward the margin of the column of mercury, thereby reducing anytendency of the mercury to flour.

A further characterizing feature of the present invention lies in thesteady and maintained imposition, upon the colloidal particles in thetailings, of a high-voltage, electrolytic pressure in the direction ofthe mercury. This may be accomplished, for example, by connecting thehigh-v Voltage terminal of a suitable source of direct current to thetailings, and connecting the lowvoltage terminal of said source to themercury column. It is important that the voltage be of the order of atleast one thousand volts, and preferably substantially higher, say, forexample, three thousand volts; and it is to be understood that the termhigh-voltage as used herein and in the appended claims is intended torefer to voltages in this category. 'Ihe effect of the electrolyticpressure is akin to the phenomena that are involved in electroplating,whereby those colloidal particles of metal which Ahave escapedamalgamation are caused to migrate rearwardly toward and into themercury, and hence into recoverable combination With the mercury. In asense, the electrolytic pressure constitutes a further means forretarding the percolating flow of the dispersed phase, thereby furtherconducing toward amalgamation.

One of the features of the invention, contributing toward the commercialfeasibility of the invention, lies in the continuous procedure whereby afixed quantity of mercury may be used and reused. The mercury iscontinuously Withdrawn from the column, subjected to a treatment whichpuries it and separates out the metal values, and returned to thecolumn. More particularly, the mercury is subjected to a continuousdistillation under vacuum.

From certain aspects, the continuous method of distilling the mercury isby itself a new and useful contribution to the art, independent of themethod whereby the mercury has become amalgamated with the metal that issought to be recovered.

The advantages and characterizing features of the present invention willbe more fully appreciated after this specication has been read, and itis pertinent to point out that amalgamation processes of the ordinarytype have heretofore been of almost prohibitive expense, both as toinstallation cost and operating cost, sometimes involving apparatusrequiring an area of sixteen hundred feet or more between theintroduction of ore and the actual metal recovery.

I achieve the foregoing objects, and such other objects as mayhereinafter appear or be pointed out, in the manner illustrativelyexemplified in the accompanying drawings, wherein- Figure 1 is adiagrammatic representation, or ow sheet, of the present method andapparatus;

Figure 2 is an enlarged, longitudinal, crosssectional View through themercury column and associated parts; and

Figure 3 is an enlarged, cross-sectional view through the retort inwhich the mercury is distilled.

The ore having been suitably crushed or otherwise mechanically reducedto a granular form capable of passing through a 10G-mesh screen, andhaving been intermixed with a liquid, preferably ordinary water, in theproportion of approximately one-thirdv solid to two-thirds liquid, it isintroduced into a hopper I0 which feeds the raw suspension into anagitating tank II. A'

turbulator or agitator I2 is continuously driven by a motor I3 toprevent sedimentation. This mixture is then passed downwardly andcontinuously into and through a colloid mill I4, driven by a motor I 5,and preferably of the type illustrated and described in myaforementioned patent application. This mill is of a character whichsuccessfully, reliably, and continuously subjects the solid particles.to an abrasion suicient to reduce the ore to a truly colloidal state inwhich the particles have a size less than one micron.

The discharge from the colloid mill passes through a conduit I6 into asecond agitating tank II in which an agitator I8 operates. Additionalliquid may, if desired, be added at this` point, or acidulatingchemicals or other aids or ingredients may be added at this point, ifdesired.

The colloidal solution passes thence through a pump I9, which is theinstrumentality for forming a flowing stream of the ore and passing thestream upwardly through a column of mercury. More particularly, thestream is directed upwardly through the loop 2B, and thence into thebottom of a steel, cup-shaped member 2l. The latter supports thecylindrical glass tube 22 in which the column of mercury 23 isaccommodated. At the top, the tube 22 carries the steel cap 24 whichcommunicates with the rubber tubing 25. For a reason presently to bepointed out, the tubing 25 is of considerable length, and for the sakeof compactness it is wound into spiral form, as shown at 26, the liquidstream ultimately emanating from the outlet 21.

That portion of the stream above the column of mercury has been referredto in the appended claims as the tailings; and it will be understoodthat the stream is at this stage ready to be discarded, with most of themetal values recovered. However, in the event that additional metalvalues or metal salts, such as tellurides or the like, are stillunrecovered, it will be understood that the stream need not necessarilybe discarded from the outlet 21 but may be subjected to furthertreatment, if desired.

In accordance with my invention, the lower portion of the member 2| (seeFigure 2) carries a disc 28 composed of metal and having a multiplicityof ne, longitudinal openings therein. For the sake of explaining thegeneral nature of the apparatus, but without intending to limit theinvention to any specic dimensions, I will mention the fact that thedisc 28 may, for example, be of approximately four-inch diameter, withapproximately two hundred fty holes or perforations therein, eachapproximately one-eighth inch in diameter. With such a disc, the glasstube 22 might be, for example, approximately four and one-half feetlong, and about ten inches in diameter; the distance between the disc`28 and the mercury level 29 might be approximately thirty-two inches.

Carried by the disc 28 is the vertically extending rod 3i), and carriedby the latter is the upwardly divergent, conical deflector 3|, and thesubstantially transverse, disc-like baiiies 32 and 33. Each of thelatter baiiies is provided kwith a plurality of holes, approximately twohundred, each about one-eighth inch in diameter. Near the lower end cfthe conical deflector 3l are a few openings 3d through which the mercurymay be drained, when necessary.

In accordance with my invention, the deflector 3l has its peripheraledge closely adjacent to the wall of the tube 22, the clearance beingpreferably no greater. than about one-fourth of an inch. The peripheriesof the baffles 32 and 33 are similarly arranged close to the tube 22.The result is that the flowing stream of ore is divided by the disc 28into a multiplicity of capillary streams which enter upwardly into themercury column and which are then deflected, as shown by the arrows ofFigure 2, toward the margin of the mercury column. These fine streams`then percolate upwardly through the mercury, and while most of thepercolation is directed toward the margin of the column, it is notprevented from disseminating itself, generally, throughout the mercury.The baiiies 32 and 33 have a retarding eITect upon the percolation, andthey also serve to minimize turbulation of the mercury. If there is anyturbulation of too great a magnitude, there is a tendency for themercury to our.

During the upward passage of the stream through the mercury, thecolloidal particles are admirably conditioned for amalgamation with themercury, and this, in fact, takes place with remarkable reliability andto a substantial degree. At the top, the reunited stream continues itsupward flow and ultimately leaves through the outlet 2l.

In accordance with my invention, the tailings are impressed with amaintained electrolytic pressure tending to cause a migration ofcolloidal particles downwardly toward the mercury. 'I'his isaccomplished by providing any suitable source of high-voltage, directcurrent, designated generally by the reference numeral 35; connectingthe high-voltage terminal by the lead 36 to the lsteel cap 24; andeither connecting the low-voltage terminal 31 to the ground, asindicated, or establishing a direct connection with the metal member 2|,and hence with the'mercury itself. One satisfactory source of currentconsists, for example, -of a standard full-wave rectier and lterequipment, such as that which is used in supplying the direct currentfor broadcasting stations, the equipment having a capability ofproducing up to about thirty-ve hundred volts and supplying a current atthat voltage of about two and one-half amperes.

The normal or articial acidity of the ore stream permits the circuit tobe completed through the tailings back to the mercury, and, in eifect, asort of electroplating action takes place whereby metal particles thathave escaped amalgamation are thrown downwardly onto and into themercury, there tobe given another chance at combining with the mercury.The distance between the level of the mercury 29 and the point ofapplication of the high-voltage potential is approximately thirty-sixinches, this having been found to -beabcut the right distance tomaintain the impressed voltage at, say, three thousand volts. Theelectrical connection is facilitated by the arrangement ofa steel ormetallic disc 38 in the lower portion of the cap 24, this disc havingholes therein and constituting what may be termed an anode screen. Theholes in the disc 38 are relatively large.

Because of the high potential that is impressed upon the stream at thescreen 38, the conduit or tube 25 is rather extended in length, ashereinbefore referred to, so that a negligible and harmless voltageremains at the outlet end, the objective being obviously to cause thecurrent to flow not toward the outlet end 2l, but through the path oflesser resistance, i. e., toward the mercury 23.

In accordance with my invention, an outlet spigot 39 connects with themember 2l at the base of the mercury column, whereby the mercury ispermitted continuously to dribble into the funnel 4B, thence downwardlythrough the U tube 4|, and into the retort 42. Since the interior of theretort is subjected to a continuous vacuum, the U tube 4l has a lengthof at least thirty-two inches, so that there is always a quantity ofmercury in the inlet arm of this tube.

The retort 42 may be of any suitable character and is preferably ofpot-shape, as shown in Figure 3, with a removable cover 43 and aremovable, cup-shaped lining 44 composed'of silica or the like. Theretort is mounted in a furnace 45 heated, for example, by means of anoilburner 42, the furnace being adequate to heat the retort toapproximately 500 C. 'Ihis is amply suflicient, under the continuousvacuum, to boil the mercury; and the mercury vapors leave the retortthrough the outlet 41 and pass downwardly through the condenser 48. Thelatter has the usual inlet and outlet openings 49 for cooling uid suchas water. The condensed liquid mercury dribbles into the container 5l]which is direct connected, as at 5i, with any suitable vacuum pump 52,the exhaust of which is shown at 53. It is this pump which maintains thedistillation at a continuous vacuum. y

Emanating from the lower end of the chamber 50 is the stand pipe 54, atleast thirty-two inches long, and having its lower end immersed in areceptacle 5.5. The mercury in the tube 54 a1- ways stands at abouttwenty-nine and one-half inches because of the atmospheric pressure uponthe-surface 56 of the mercury in the receptacle 55. An overflow outletpipe 51 communicates with a pump 58, which in turn continuously returnsthepuried mercury back into the column through the conduit 59. r

`It will thus be seen that the mercury is continuously withdrawn fromthe column; subjected to a rcontinuous distillation under vacuum; andreturned in purified condition to the mercury column. At the same time,the metal that has been -amalgamated with the mercury is separated outin the retort 42, inasmuch as the temperatures there developed areinsufficient to boil off the metal.' The result is that the mercury,constituting a xed quantity, and excepting only such small amounts asmay be required'for makeup purposes, is used and reused and isv kept ina continuously pure condition, admirably suited for amalgamation withthe colloidal metal particles percolating through it.

-The metal which is sought to be recovered collects in a sort ofsponge-like mass at the bottom of the lining 44 in the retort 42. Whilethe quantity will vary, depending upon the particular ore, and the sizeof the apparatus, mercury column, Voltage, etc., I will state merely byway of example that an apparatus ofthe approximate dimensionshereinspecied has a capacity of approximately twenty-four tons of ore per day,and that as much as sixty ounces of gold have been successfullyrecovered, in the form of a spongy mass in the lining 44, at theexpiration of a three-day operating period. This amount of recovery isatruly remarkable accomplishment when it is borne in mind that the costof operating the present apparatus is as low as 2`2 per ton, and that adistance no greater than fifteen feet is required between the hopper l0(at which the raw ore is deposited) and the retort 42 (in which thevaluable metal is recovered).

It will be understood that the present drawings are merely illustrative.If desired, the column of Vmercury may be made longer and wider,provided that suicient strength is imparted `to thevessel which holdsit. It hasbeen found satisfactory to employ a series of mercury columnsin-parallel. Also, the voltages may be varied to suit requirements, andnumerousrother details may be altered or modied under dif,- erentoperating conditions.

In general, it will be understood that changes in the details, hereindescribed and illustrated for the purpose vof explaining in the natureofmy invention, may be lmade by those skilled in the art withoutdeparting from the spirit and scope of n.

the invention as expressed in the appended claims. It is, therefore,intended that these details be interpreted as illustrative, and not in alimiting sense.

Having thus described my invention, and illustrated its use, what Iclaim as new and desire to secure by Letters Patent is:

l. In the herein described ore-recovery process, the steps which consistin colloidizing the ore in a liquid medium, percolating it through abody of mercury, and exerting upon the tailings a continuous,high-voltage, electrolytic pressure toward the mercury, said highvoltage being in thc range between approximately 1000 and 3000 vo-ts.

2. In the herein described ore-recovery process, the steps which consistin colloidizing the ore in a liquid medium, percolating it through abody of mercury, exerting upon the tailings a continuous,

mercury, said high voltage being in the range between approximately 1000and 3000 volts, and continuously distilling the mercury to purify it andto recover the metal amalgamated therewith.

3. In the herein described ore-recovery process, the steps which consistin colloidizing the ore in a liquid medium, percolating it througha'body of mercury, retarding the percolation to prevent louring of themercury and to conduce toward amalgamation, and exerting upon thetailings a continuous, high-voltage, electrolytic pressure toward themercury, said high voltage being in the range between approximately 1000and 3000 volts.

4. In the herein described ore-recovery process,

I the steps which consist in colloidizing the ore in a liquid medium,percolating it upwardly through a column of mercury, guiding thepercolation toward the margin of the mercury columnto prevent flouring,and exerting upon the tailings a continuous, high-voltage, electrolyticpressure toward the mercury, said high voltage being in the rangebetween approximately 1000 and 3000 volts.

5. In the herein described ore-recovery process, the steps which consistin colloidizing the ore in a liquid medium, percolating it upwardlythrough a column of mercury, guiding the percolation toward the marginof the mercury column to prevent ouring, retarding the percolation toconduce toward amalgamation, and exerting upon the tailings acontinuous, high-voltage, electrolytic pressure toward the mercury, saidhigh voltage being in the range between approximately 1000 and 3000volts.

6. In the herein described ore-recovery process, the steps which consistin forming a owing stream composed of the ore oolloidized in a liquidmedium, passing the stream upwardly through a column of mercury, andimpressing upon the stream as it leaves the mercury a maintained highelectric potential relative to the mercury, said high electric potentialbeing in the range between approximately 1000 and 3000 volts.

7. In the herein described ore-recovery process, the steps which consistin forming a owing stream composed of the ore colloidized in a liquidmedium, dividing the stream into a multiplicity of capillary streams andcausing the latter to percolate upwardly through a column of mercury,and impressing upon the reunited stream as it leaves the mercury amaintained high electric potential relative to the mercury, said highelectric potential being in the range between approximately 1000 and3000 volts.

8. In the herein described ore-recovery process, the steps which consistin forming a flowing stream composed of the ore colloidized in a liquidmedium, passing the stream upwardly through a column of mercury,impressing upon the stream as it leaves the mercury a maintainedhighelectric potential relative to the mercury, said high electric potentialbeing in the range between approximately 1000 and 3000 volts, andcontinuously withdrawing the mercury from said column, subjecting it todistillation to separate it from the metal amalgamated therewith, andreturning it in purified form to the column.

9. In ore-recovery apparatus of the character described, a column ofmercury, means for colloidizing the ore in a liquid medium, means forpercolating it through said mercury, and means for exerting upon thetailings a continuous, highvoltage, electrolytic pressure toward themercury,

said high voltage being in the range between approximately 1000 and 3000volts.

10. In ore-recovery apparatus of the character described, a column ofmercury,v means for co1- loidizing the ore in a liquid medium, means forpercolating it through said mercury, and means for exerting upon thetailings a continuous, highvoltage, electrolytic pressure toward themercury; said last-named means comprising an insulating vessel for themercury, a source of highvoltage, direct current, said high voltagebeing in` the range between approximately 1000 and 3000 volts and meansfor connecting the tailings and the mercury to the high and lowterminals of said current source, respectively.

11. In ore-recovery apparatus of the character described, a column ofmercury, means for colloidizing the ore in a liquid medium, means forpercolating it through said mercury, means for exerting upon thetailings a continuous, highvoltage, electrolytic pressure toward themercury, said high voltage being in the range between approximately 1000and 3000 volts and apparatus for continuously distilling the mercury topurify it and to recover the metal amalgamated therewith.

12. In ore-recovery apparatus of the character described,` a column ofmercury, means for colloidizing the ore in a liquid medium, means forpercolating it through said mercury, means for exerting upon thetailings a continuous, highvoltage, electrolytic pressure toward themercury, said high voltage being in the range between approximately 1000and 3000 volts, and apparatus for continuously withdrawing the mercuryfrom said column, subjecting it to distillation under vacuum, andreturning it in purified condition to said column.

13. In ore-recovery apparatus of the character described, a column ofmercury, means for colloidizing the ore in a liquid medium, means forpercolating it through said mercury, means for exerting upon thetailings a continuous, highvoltage, electrolytic pressure towardl themercury, said high voltage being in the range between approximately 1000and 3000 volts, and means for retarding the percolation to preventflouring of the mercury and to conduce toward amalgamation.

14. In ore-recovery apparatus of the character described, a column ofmercury, means for colloidizing the ore in a liquid medium, means forpercolating it through said mercury, means for exerting upon thetailings a continuous,.highvoltage, electrolytic pressure toward themercury, said high voltage being in the range between approximately 1000and 3000 volts, and means for retar-ding the percolation to preventouring of the mercury and to conduce towardv amalgamation; saidlast-named means comprising spaced, perforated bales arrangedtransversely across the mercury column.

15. In ore-recovery apparatus of the character described, a column ofmercury, means for colloi-dizing the ore in a liquid medium, means forpercolating it through said mercury, means` for exerting upon thetailings a continuous, high- Voltage electrolytic pressure toward themercury, said high voltage being in the range between approximately 1000and 3000 volts and deflecting means at the bottom of the mercury columnfor guiding the entering ore toward the margin of the column so as toprevent flouring.

ELMAN B. MYERS.

